1. Field of the Invention
The present invention relates to a SiO.sub.2 - and ZrO.sub.2 - based ceramic fibers. The invention furthermore relates to the process for preparing said ceramic fibers.
More in particular, the field of the present invention relates to a process for preparing ZrO.sub.2 - and SiO.sub.2 - based ceramic fibers which comprises the steps of:
a) preparing a solution formed by the compound of formula (I) EQU Zr(OR.sup.1).sub.4 (I)
where R.sup.1 is an alkyl or aryl,
by the compound of formula (II) EQU Si(OR.sub.2).sub.4 (II)
where R.sup.2 is an alkyl or aryl,
by an organic solvent and by an acid, preferably maintained at a temperature comprised between 0.degree. and 100.degree. C., and hydrolysis, with consequent polymerization of the compound of formula (I) and of the compound of formula (II),
b) drawing of the solution obtained with said step (a),
c) heating of the fibers obtained with said step (b) until the crystallization of ZrO.sub.2 and SiO.sub.2 is obtained. The ceramic fibers obtained according to the invention have a vast range of utilization, since they are particularly resistant to high temperatures, especially when they contain a relatively high percentage of ZrO.sub.2. In particular, said fibers have considerable mechanical properties at high temperatures, and this allows to use them as reinforcement structure, for example embedded in the casting of metallic materials, in particular of aluminum-based light alloys, or in composite materials, even basic ones, with a ceramic matrix.
By way of example, said fibers can also be used in the manufacture of catalytic elements.
The above is in summary the main fields of industrial utilization of the invention, but said fields do not constitute a limitation to the scope thereof, since the process according to the invention and the ceramic fibers obtained, in particular as described and claimed hereafter, can be advantageously used in any other equivalent field in which ceramic fibers adapted to withstand high temperatures are produced with a process which entails the steps (a), (b) and (c) described above.